TryHackMe — Public Key Cryptography Basics | Cyber Security 101 (THM)

Common Use of Asymmetric Encryption

Asymmetric encryption is mainly used to exchange keys for faster symmetric encryption, as asymmetric methods are slower. Here’s how it works:

Analogy: Imagine you need to send a secret code (symmetric key) securely. Your friend gives you a lock (public key) that only they can unlock (private key). You lock the code in a box and send it. Only they can open it with their key, allowing you to communicate securely from then on.

Mapping:

• Secret Code = Symmetric Key and Cipher
• Lock = Public Key
• Lock’s Key = Private Key

In practice, additional cryptography like digital signatures is used to verify identities.

Questions and Answers

1. In the analogy presented, what real object is analogous to the public key?

• Lock

RSA

RSA is a public-key encryption method for secure communication over insecure channels, relying on the difficulty of factoring large numbers.

The Math Behind RSA: RSA’s security is based on the challenge of factoring large numbers. While multiplying two large primes is easy, finding their factors from the product is difficult.

Example:

• Prime 1: 982451653031
• Prime 2: 169743212279